Subject: Re: [PATCH] Disable bgworkers during servers start in pg_upgrade
To: Bruce Momjian <bruce@momjian.us>, Daniel Gustafsson <daniel@yesql.se>
Cc: Julien Rouhaud <rjuju123@gmail.com>, Michael Paquier
 <michael@paquier.xyz>, Jehan-Guillaume de Rorthais <jgdr@dalibo.com>,
 Andres Freund <andres@anarazel.de>,
 PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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From: Denis Laxalde <denis.laxalde@dalibo.com>
Message-ID: <71b7869f-af55-ae33-afba-cfd4de35b944@dalibo.com>
Date: Thu, 26 Aug 2021 16:07:40 +0200
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Bruce Momjian a écrit :
> On Thu, Aug 26, 2021 at 03:38:23PM +0200, Daniel Gustafsson wrote:
>>> On 26 Aug 2021, at 15:09, Bruce Momjian<bruce@momjian.us>  wrote:
>>> On Thu, Aug 26, 2021 at 03:24:33PM +0800, Julien Rouhaud wrote:
>>>> .. I still think that
>>>> changing bgworker_should_start_now() is a better option.
>>> I am not sure.  We have a lot of pg_upgrade code that turns off things
>>> like autovacuum and that has worked fine:
>> True, but there are also conditionals on IsBinaryUpgrade for starting the
>> autovacuum launcher in the postmaster, so there is some precedent.
> Oh, I was not aware of that.
> 

If I understand correctly, autovacuum is turned off by pg_upgrade code 
only if the old cluster does not support the -b flag (prior to 9.1 
apparently). Otherwise, this is indeed handled by IsBinaryUpgrade.